The present disclosure relates to methods and devices for occluding a body lumen. For example, at least one embodiment is directed to a device and method for occluding the left atrial appendage of the heart.
Atrial fibrillation (AF) is the most common sustained cardiac arrhythmia affecting over 5.5 million people worldwide. AF is the irregular, chaotic beating of the upper chambers of the heart. Electrical impulses discharge so rapidly that the atrial muscle quivers or fibrillates. Episodes of AF may last a few minutes or several days. A serious consequence of AF is ischemic stroke. It is estimated that up to 20% of all strokes are related to AF. Most AF patients, regardless of the severity of their symptoms or frequency of episodes, require treatment to reduce the risk of stroke. In patients with AF, blood tends to pool and form clots in an area of the heart called the left atrial appendage (LAA). The LAA is a pouch-like extension located in the upper left chamber of the heart. A blood clot that breaks loose from this area may migrate through the blood vessels and eventually plug a smaller vessel in the brain or heart resulting in a stroke or heart attack. Clinical studies show that the majority of blood clots in patients with AF are found in the LAA (see Blackshear J. L., Odell J. A., Appendage Obliteration to Reduce Stroke in Cardiac Surgical Patients with Atrial Fibrillation. Annals of Thoracic Surgery, 1996;61:755-759).
Treatment of AF may include surgically closing the LAA, epicardial LAA ligation, or delivering a device or mechanism across or into the LAA in order to occlude it. Occlusion devices for addressing AF typically utilize a metallic “cage” and/or fabric graft, which, when deployed, form a circular shape across and/or within the LAA. They are delivered to the treatment site via a catheter system (see, e.g., U.S. Pat. No. 6,994,092 to van der Burg et al.; U.S. Pat. Nos. 6,652,556 and 7,727,189 to Van Tassel et al., the entire contents of all of which are incorporated herein by reference).
In FIG. 1, a cross-sectional view of the human heart is shown. FIG. 1 also depicts a common technique whereby a catheter is threaded through the vasculature and into the heart to deliver an occlusion device to the LAA. Ideally, when the device is properly positioned within the LAA the occlusion device forms a seal with the wall of the LAA in order to prevent emboli or blood clots from passing back into the blood stream. Many known occlusion devices (an example of which is shown in PRIOR ART FIG. 2a), however, are equipped with frameworks that while sufficient to support a filter or membrane, have insufficient circumferential and/or radial strength to resist the distortive forces (indicated by arrows in PRIOR ART FIG. 2b) that the LAA exert on the occlusion device. As a result, the seal such devices form with the interior wall of the LAA is compromised as the framework is bent into a more elliptical shape by the LAA. As a consequence, such devices may allow some material to exit the LAA and re-enter the blood stream.
Even where such known occlusion devices maintain their seal despite being distorted, the irregularity of the device's shape can also result in flattening during recapture of the device into the delivery catheter.
Many occlusion devices may suffer from effects of foreshortening. Foreshortening during expansion of expandable occlusion devices may negatively affect deployment accuracy. For example, an expandable occlusion device that foreshortens during expansion may tend to be more difficult to deploy since the position of the distal end of the device changes by shrinking back toward the proximal end as the device expands (i.e., the longitudinal distance between the distal end and proximal end shortens upon expansion). Deployment accuracy may be improved by reducing or eliminating foreshortening.
As such, there remains a need for an occlusion device that has improved circumferential strength without foreshortening or excessive distortion.
The above reference to and/or description of documents is not intended to constitute an admission that any patent, publication, or other information referred to herein is “prior art” with respect to this disclosure. In addition, this section should not be construed to mean that a search has been made or that no other pertinent information as defined in 37 C.F.R. §1.56(a) exists.